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LF: Frequency / drift measurements (using SL, for G0BND)

To: RSGB LF Group <[email protected]>
Subject: LF: Frequency / drift measurements (using SL, for G0BND)
From: wolf_dl4yhf <[email protected]>
Date: Sat, 06 Aug 2011 20:19:06 +0200
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Hi Graham,

I tried to reply to you pm address, but your provider keeps bugging me with failed deliveries and error messages like

"We have limits for how many messages can be sent per hour and per day."
Nnnngrrrrr...

My excuse to the group for hijacking the reflector for the following response, which should have been sent directly.

You asked:
>>>
Can  you  advise  on settings
 
I need  to  measure  the  drift  of TX , using  my  RA1778 (high  stab master osc)  / M-Delt 4   96K  sound   card  , to  produce audio   frequency  of  1500 Hz
 
Ideal  would be  to  show   1 HZ  or  2 Hz   full  screen  (  1499  >  1501) or     (  1499.5  > 1500.5) 
 
If  I zoom  in  on the   frequency , the  display becomes  very  ''block like''  
 
The  measurements  need  to  be  60  seconds apart , to  give a  drift  from  cold  plot
 
Q  Is  it  possible to make  such  measurements   ?
<<<

If the measurements may only be 60 Hz apart, the normal FFT will not give the ultimate resolution (thus the screen will look block like when zooming in). With a measurement time of 60 seconds, the best you can get is something around 1/60s = 16.6 mHz effective resolution.

There are two alternatives:
A - use the experimental "time/frequency reassigned spectrogram" (it gives a readout resolution which is MUCH better than the FFT resolution dictated by the FFT length). Details about this rarely used function are here:

http://www.qsl.net/dl4yhf/speclab/ra_spectrogram.htm



B - use the 'phase-and-amplitude' monitor. If only produces numeric output (no waterfall-like display), but you could plot the frequencies in the 'watch window'. The phase/amplitude monitor function can also measure frequencies. Details are here:

http://www.qsl.net/dl4yhf/speclab/phase_amplitude_monitor.htm


For a start, the reassigned spectrogram may be the easier alternative. There are a few preconfigured settings which you can recall through the 'Quick Settings' menu.

Hope this helps,
  73,   Wolf .
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